Of the vehicles entering a particular interchange from the south, 40 percent, on the average, want to go to the west, 10 percent to the east, and the remainder straight through. What is the probability that of eight entering cars, half will want to go west and half straight? What is the distribution of the west-bound number X1 , the east-bound number X2 , and the north-bound number X3 out of eight vehicles entering from the south? What is the marginal joint distribution of X1 and X3 ? What is the marginal distribution of the number of cars (out of eight) turning to the west? What is the probability that more than half will want to turn to the west (i.e., to the left)? Such questions are of concern to the interchange designer who must balance cost of interchange versus cost of traffic delays. (Assume independence among driver desires throughout.)